Problem with inducer pressure failsafe system (Payne PG9MAA048100)


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Old 01-04-13, 03:52 PM
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Problem with inducer pressure failsafe system (Payne PG9MAA048100)

Good day,

I am having trouble with my furnace firing up. This problem has been re-occurring intermittently sense the furnace was installed 10 years ago. For the past three years I have been using geothermal for primary heat so the Payne has been just sitting there as back up. I decided to fire it up last week just to test it.. no go.. it would not fire up.. Here are some key points:

  • The furnace is using propane.
  • I checked all condensate drain hoses and trap.. all are clean.
  • I checked all pressure switch hoses.. they also are clean.
  • I checked the exhaust vent and it is clear. I could not get at the intake air pipe to check it.
  • This furnace has a pressure switch with two rubber hoses attaching to it. The bottom hose goes to the collector box. The top hose goes to a "T" fitting, one side goes to the fuel regulator and the other goes to the bottom of the combustion chamber.
  • If I disconnect the rubber hose from the top of the pressure switch and plug it.. the furnace will fire up. Once running, I can plug the rubber hose back into the top of the pressure switch and the furnace will keep running until target temp is met but then it fails to re-start after that.
  • If the furnace is running and I disconnect the rubber hose from the bottom of the pressure switch, the furnace will shut down.

Thanks for any leads you may be able to provide!

Jeff
 
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Old 01-04-13, 05:11 PM
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Check your venting system.
 
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Old 01-04-13, 05:32 PM
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I did check the exhaust but will check intake tomorrow.. thank you for the reply.

Jeff
 
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Old 01-05-13, 10:14 AM
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I checked the venting system.. all pipes are clear.

There is quite a vacuum being generated in the combustion chamber for some reason. If I remove the combustion chamber cover, the furnace fires up.

Another factor that could shed some lite.. the furnace installer left a cap off of the port used for left hand combustion air intake. I installed the cap years ago and the furnace worked but it was very intermittent on firing up from this point on. The photo below visualizes this point.

I am starting to wonder if the size of the combustion air pipes is too small?

Jeff

 
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Old 01-05-13, 11:17 AM
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you do need to have that cap in place (don't have to if your furnace is listed for single pipe installation). Your venting system may be too small as you stated. Make sure it has the proper slope all the way from the termination to the furnace. Do you have the installation manual? It will tell you how far of a run the venting system can be at a certain size.
 
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Old 01-05-13, 12:39 PM
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Hum.. I feel like an ass now..

Your original advice was spot on. The combustion pipe had a mouse nest and three dead mice in it.. The airflow was restricted but not totally blocked and that through me a little but after some additional work.. I was able to clear it out and the furnace works fine.

Thanks for the information !!!
 
 

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